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Communication Security: Wireless • Chapter 4 207

the number of wireless hosts transmitting on the WLAN, and the number of IV
retransmissions due to 802.11 frame collisions, the WEP key could be cracked
within a couple of hours. However, if an attacker attempts to listen to a WEP-pro-
tected network at a time of low network traffic volume, it would take significantly
longer to get the data necessary to crack WEP.

EXERCISE 4.01

CONFIGURING STATIC WEP KEYS

ON WINDOWS XP AND WIFI-COMPLIANT APS
As a minimum requirement, static WEP keys should be configured on
APs and wireless clients. If the hardware is WiFi compliant, a minimum
of 64-bit encryption can be set (a 40-bit key with a 24-bit IV). However,
if available on the hardware, 128-bit encryption should be selected (a
104-bit key with a 24-bit IV). Some vendors now provide 256-bit WEP.
However, this is proprietary technology and, because it is not standard,
may not be interoperable between the different vendors.
Most APs allow for configuration of up to four different WEP keys
for use on a wireless network. However, only one of these WEP keys can
be used at one time. The reason for configuring up to four WEP keys is
to provide an easy means for rolling over keys according to a schedule.
Figure 4.10 shows the WEP Key configuration property for a Linksys
WAP11.

Figure 4.10 Configuring WEP Keys on a Linksys WAP11

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